Index: test/BaseJsTest.h
===================================================================
--- a/test/BaseJsTest.h
+++ b/test/BaseJsTest.h
@@ -100,22 +100,22 @@
   {
     throw std::runtime_error("Unexpected error: " + message);
   }
 };
 
 class ThrowingFileSystem : public AdblockPlus::FileSystem
 {
 public:
-  std::shared_ptr<std::istream> Read(const std::string& path) const
+  FileSystem::IOBuffer Read(const std::string& path) const
   {
     throw std::runtime_error("Not implemented");
   }
 
-  void Write(const std::string& path, std::istream& content)
+  void Write(const std::string& path, const FileSystem::IOBuffer& content)
   {
     throw std::runtime_error("Not implemented");
   }
 
   void Move(const std::string& fromPath, const std::string& toPath)
   {
     throw std::runtime_error("Not implemented");
   }
@@ -144,27 +144,27 @@
   {
     throw std::runtime_error("Unexpected GET: " + url);
   }
 };
 
 class LazyFileSystem : public AdblockPlus::FileSystem
 {
 public:
-  std::shared_ptr<std::istream> Read(const std::string& path) const
+  IOBuffer Read(const std::string& path) const
   {
     std::string dummyData("");
     if (path == "patterns.ini")
       dummyData = "# Adblock Plus preferences\n[Subscription]\nurl=~fl~";
     else if (path == "prefs.json")
       dummyData = "{}";
-    return std::shared_ptr<std::istream>(new std::istringstream(dummyData));
+    return IOBuffer(dummyData.cbegin(), dummyData.cend());
   }
 
-  void Write(const std::string& path, std::istream& content)
+  void Write(const std::string& path, const IOBuffer& content)
   {
   }
 
   void Move(const std::string& fromPath, const std::string& toPath)
   {
   }
 
   void Remove(const std::string& path)